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B. SCOTT. TELEPHONE EXGHANGE SYSTEM AND APPARATUS.

No. 253,316. Patented Feb. A1882.

SUBSCRIB-ERS STATIONS.

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UNITED STATES PATENT OFFICEo GEORGE B. SCOTT, OF BROOKLYN, NEW YORK,ASSIGNOR TO EUGENE F. PHILLIPS, OF PROVIDENCE, RHODE ISLAND.

TELEPHONE-EXCHANGE SYSTEM AND APPARATUS.

SPECIFICATION forming part To all whom may concern:

Be it known that I, GEORGE B. SCOTT, of

l the city of Brooklyn, in the county of Kings nication as hasheretofore been attained by the use of double wires, of which one isdevoted exclusively to calling or'signaling purposes. I thereby obviatethe cost of the expensivelyinsulated special wire and all that pertainsessentially thereto in the way of line care.

Another object is to signal over asingle wire by direct telephoniccommunication between subscribers and central stations, therebyobviating the cost of annunciators at the central stations, the care andattention incident thereto, and more particularly obviating the delayand confusion incident to the operation of annunciators, involving, asthey do, great nicety of adjustment, and being specially liable totemporary derangement and uncertain operation.

Another object is to enable the business at the central station to beconducted in silence by the operatives, thereby securing promptattention to business and obviating the errors naturally incident toloud and hurried calling, and also to render it practicable tocarry outa reliable registry of service to each subscriber, so that each may becalled upon to pay in proportion to his actual employment of the system,thus tending to unburden the system of much, that is trivial andreducing its operations to a practical business basis; also, to maintainbetweeuthe subscriber and the central station a signaling and telephonic.com-

vmunication which is not dependent upon the manipulation of switches bysubscribers, whereby I obviate the delays and inconveniencesv incidentto switch-setting at the hands of careof Letters Batent No. 253,316,dated February 7, 1882. Application filed February 11, 1880.

less or inexperienced persons. This feature, so far as my knowledgeextends, has never before been attained.

For the attainment of these ends my invention, broadly stated, consistsof a telephonic exchange system embodying a series of independentsubscribers wires or circuits, all branching out and normally inconnection with a central receiving-instrument at the central office orstation, but adapted to prevent the currents, ora 'sufticientportiouthereof, from being diverted into the branch circuits not in use, andprovided with apparatus to receive and transmit signals at said centraloffice or station; and, further, in a telephonic exchange system, aseries of closed circuits centering in and passing through a singlecentral instrument and resistance in the said circuits to confine theelectric currents, or the main portions thereof, in the circuit passingthrough said central instrument; and, further, in a telephonic exchangesystem, a series ofcircuits, all unitingand passing through a singlecentral instrument, and adapted to confine the main portion of thecurrent tothe circuit passing through said central instrument, combinedwith electric switches adapted to be operated from the central office toclose the distant end of the said circuit through a branch circuit orelectrical connection to ground, to enable the usual signals to beoperated from the central oflice; and, further, in the combination, witha series of wires, each communicating with one ormore subscribers andradiating from a ground-wire at the central station, of alistening-telephone connected with said ground-wire and a highresistance nearthe terminus of each subscribers wire.

The gist of the several features of invention thus far stated is inproviding such a high resistance or its equivalent at the outer end ofeach subscribers circuit or wire that telephonic communication isassured between any one subscriber and the ground-wire telephone at thestation, regardless of the central connection with the same ground-wireof the other subscribers wires.

For telephonic communication with the central station and betweensubscribers, an electric power of the ordinary character is onlyrequired--as, for instance, that involved with a Blake transmitter; butfor operating each subscribers signal apparatus from the central stationa higher electric power is necessary in order to overcome the highresistance on the subscribers wires; and for the reason that my system,as a novel feature, involves the employment of two distinct electriccurrents of different power I term it the duplex sys tem. The source ofthe high electric power may be derived from chemical batteries or fromdynamo-electric apparatus; and in that connection my invention furtherconsists of a series ofsnbscribers wires, a telephone, a highresistance, and a signaling apparatus at the terminus of each wire, anda central station having a ground-wire and listening-telephone common toall the wires, in combination with a battery or a dynamo-electricmachine and suitable means for applying the electric power therefrom toany of the wires for overcoming the high resistances thereon andoperating the calling-signal. In this combination it is to be understoodthat the telephone at each subscribers station necessarily involves somemeans whereby an operative electric current is aiforded for transmissionof sound-vibrations to the central station, said current, howeverderived, being one of the two currents of different powers employed inmy novel duplex system.

My invention further consists in a sub-combination as follows, viz: aseries of wires for telephonic communication radiating from a centralstation, each connecting with a subscribels signal apparatus locatedbetween a high resistance and ground, in combination with means at thecentral station for obtaining an electric current of sufficient power toovercome said high resistance and means for applying said current to anyand all of said wires for operating subscribers signals. In this laststated combinationI do not limit myself to any special telephonicsystem, for although it is of great importance in the particular novelsystem herein disclosed,Iam well aware of the value of the principleinvolved, and realize the practicability ofits application in othersystems.

Under my present system more than one subscriber can be served through asingle wire, in which case the high resistance is located with theterminal subscriber, and therefore all the signals on that wire will besounded simultaneously, requiring each to determine as to his ownparticular cal], and causing the nearest subscriber, while using theline, to automatically cut off those beyond, and also exposing any ofthe outermost subscribers, when using the line, to interruptions fromany subscribers between them and the central station. It is therefore ofspecial importance that I obviate, as hereinafter described, allmanipulation of switches.

Certain other minor features of invention will be hereinafter fullyspecified.

To more particularly describe my invention, I will refer to theaccompanying drawings, in which-- Figure 1 represents the apparatusemployed at a central station. Figs. 2 and 4 represent the apparatusemployed at terminal subscribers stations. Fig. 3 represents theapparatus employed at an intermediate subscribers station. The severalstations are shown with proper line-wire connections.

I will first describe the apparatus at the central station.

I employ, as heretofore, connecting'bars A,

proportioned to the number of subscribers to be served therewith andalso to the extent of their business. As a rule, seven or eight sets ofbars will be ample for fifty subscribers. Heretofore a singleconnecting-bar has been employed for receiving the plugs of twoswitch-cords, respectively connected with the switches of wires of twoparties in communication. My connecting-bars are of a novel character,in that two separate bars electrically coupled together and to a batteryconstitute a set of connecting-bars. These pairs or sets of bars operateas one bar, so far as a relates to the mere connection of two switches;but they are also capable of being coupled to a battery for applying itselectric power to the line over which communication is desired. Asanother novel feature in this connection, I employ an electricindicator, A, which is interposed between the bar-battery and the bars,whereby at a glance it may be determined whether the bars to which itbelongs are in service. As will be hereinafter more fully shown, thereis no high resistance on lines which are coupled and opened totelephonic communication via the central ofiice, and therefore thebar-battery has sufficient power to deflect the galvanometer A forshowing that the lines which are coupled through the bars are occupied,and when thereafter those lines resume their normal condition, with thehigh resistances thereon, the bar-battery being incapable of suflieientcirculation to longer hold the galvanometer-needle, it falls back tozero, indicating that telephonic service through that set of bars hasterminated. This indicator A may be variously constructed; but a simpleform of galvanometer will serve the purpose, its needle indicatingpromptly whether the barbattery is in open or closed circuit; and as anadditional novel feature I employ a hand-indicator, A, which is to bepushed to one side when its particular set of bars is putinto serviceand to the opposite side when the serviceis terminated, affordingpositive information to the switchman as to disengaged bars, andrendering it obviously unnecessary to watch all the electric indicators.Each of these handindicators operates as a shield over the proper numberof its connecting-bars when said bars are in use.

The several line-wires enter the station as heretofore, and of these butthree are shown 10. by wire I), which extends through alisteningtelephone, D, and thence to ground. The keys a are normally outof circuit with battery a so that communication is always open over allthe line wires through said keys,

thence through the switches, and thence to and through thelistening-telephone to ground. On pressing either keythe full force ofbattery a is applied to its liuewire for signaling purposes, ashereinafter more fully explained.

The telephone-listener, being always in communication with all thesubscribers wires, is ready to respond as directed in each case. I

The mode of connecting any two line-wires by meansofthe usualswitch-cords, c, is effected by placing them in the switches and theconnecting-bars,-thereby taking in the small battery, and the presenceof a switch-cord plug cuts off communication of theline-wire to whichthe switch belongs with thelistening-telephone 0 at the central station.

1 will now proceed todescribe a terminal snbscribcrs station on one ofthe linefwires, illustrated fully in the drawings.

It will be remembered that all the line-wires atthe central stationterminate in a groundwire tapped by a listening-telephone common to allthe wires. ,As usual, the outer end of each linewire terminates atground; but on entering a subscrihers station it connects with a springswitch-lever, E, provided with a hook at its end for carrying, as usual,the telephone F, which, by its weight, maintains said lever against itslower stop, d, from which the linewire is practically continued, as atd, to and through a high-resistance relay, G, thence through asignal-bell,H, and thence to ground. This relay G, as employed by me,constitutes an electric switch'adapted to be operated from the centraloflice fonenabling the required callingsignals to be made from saidoffice, whether there be one or more subscribers on any one wire orcircuit. While I prefer to locate the high resistance on the line sideof the hell, I

do not limit myself thereto because when in- 5 5 termediate stations areprovided for, as hereinafter explained, said stations have no separatehigh resistances, but rely upon the resistance at the terminal stationon the same circuit, and therefore insuch circuits the resist- 6'o anceis between the signal-bell of an intermediate station and the ground,instead of being on the line side of sa'idbell. The line-wire projectiond. is connected oiropposite sides of the resistance by wirescl and anarmature, e,whereby, when the full force of theheavy battery at thecentral station is applied to the line-wire,

the high resistance of the relay G-say of five thousand ohms-is so farovercome as to cause the movement of the armature e to its stop 6, thusproviding a direct but slightly intermittent passage for the heavybattery-curren t, having ample power to work the bell according to themovement of the proper line-signal key at the central station,

The high-resistance relay may be constructed of very fine German-silverwire, and thus be neitheroverexpensivenorbulky. Thebellpreferred by usis one of the single-stroke variety.

The signal having been received, the telephoneis lifted from its hook,whereupon the switch-lever E is lifte y its spring from its lower stop,d, thus cutting off the ground-connect-ion via the line through theresistance G and opening up the requisite ground-connection, as follows:

The switch-lever E has on its upper surface a wedge-shaped spur, ascommonly employed for operating with a double spring-stop,as shown atf,the opposite sides of which respectively connect with a Blaketransmitter, I, (or other suitable apparatus and through it with thetelephone F, and thence in the usual manner to ground m'a wire g, thusplacingthe sub- -scriber in telephonic communication with thecentralstation, and with the calling party when theproper switch-boardconnections have been made at the central office.

For calling the central station the subscriber has only tolift histelephone and speak through it or the transmitter, finding always alistener on duty at the central oflice. Itis during this calling ofsubscribers that the high'resistance performs its important functions.If, say, fifty wires are employed in one series, each with, say, fivethousand ohms, the resistance to be overcome on anyone wire through thetelephone when grounded at its outerend will not exceed about one'hundred ohms, and such a lowresistance does not impair theconversational capacities of the line. Were it not for these highresistances on each of these Wires, no practical results could beattainedas, for instance, when fifty wires are employed, all of themwould be practically open to ground at their outer ends, and thereforefree to be traversed by the telephone vibrations from any one telephone;but when thus guarded by the resistances, each wire serves practicallythe same purpose as if it were not one of a series of wires having aground and a listening telephone commcn to all of them.

Although it is preferable to have a single subscriber for each wire, twoor more can be located thereon with no disadvantages other than sueh'asareincident to other systems. The liability of simultaneous calls lromtwo or more subscribers to the listening-telephone at the centralstation and the possibility of confusion incident thereto are presentinthe special signal-wire system, and also in my system, whether each wireis or is not limited to one subscriber; but when Lplace more than one,

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subscriber on a wire no persons beyond the party using the line cancontribute to this confusion, for they will be cut off from the centralstation so long as an intermediate one is in use. In calling from thecentral station all the signals on one wire will be sounded asheretofore under similar conditions, requiring special signals andattention thereto from each subscriber, whereas on a single-subscriberwire a sounding-signal of any kind is only required.

An intermediate subscribers apparatus is illustrated in Fig. 3. [t hasno high resistance, that being required only at the terminal station.Its signal apparatus H occupies a position on the line via thespring-switch lever E, its lower stop, (1 and wire d thence to theoutward line toward the terminal subscribers station. The telephone andtransmitter are precisely the same as at terminal stations.

For cutting oh" the outer line and attaining a local ground-connection athumb-switch may be employed; but as the careless failure to properlyreturn the switch to its normal position would keep all subscribersbeyond out of communication with the central office, I-have provided anautomatic spring-switch, K,which is located abo e the outer end of theswitchlever E, on which the telephone I is supported when not in use.This switch K is wired at h to wire g, leading from the telephone to theline-wire beyond, and its stop z" is wired direct to ground. The springof switch K maintains it normally in a depressed position away from itsstop, and it is lilted by the telephone switch-lever E, with which ithas an insulated contact, so that when the telephone is taken from itsbook the telephone ground-connection is attained via wires g and it,through switch K and the ground-wire leading from stop 1'.

As a means for readily indicating to all subscribers the electriccondition of a line-wire common to several subscribers, I apply at eachsubscribers apparatus an electric indicator of a simple character,similar to the indicators A employed at the central station.

The sub-combinations deemed by me to be novel in my apparatus are asfollows: an electric signal-bell and ground-wire connection guarded onthe line side of the bell with a high resistance; on a telephonicline-wire provided at its outer end with a high resistance and acalling-signal, a relay by which said high resistance is cut out foroperating the signal; at an intermediate subscribers station on atelephonic line-wire provided at its outer end with a high resistance, aspring switchlever maintained in a depressed position by the weight of atelephone hung thereon, and a switch to ground, automatically controlledthrough they utomatic movement of the spring switch-lever when relievedfrom the telephone and when loaded therewith; in the centralstationapparatus, the combination, with each pair of connecting-bars, of anelectric indicator for disclosing the termination of service, and also ahand-indicator mounted on'or near the connecting-bar board, and arrangedwith relation to its particular set of connecting-bars so as to be underthe eye of the switchman while on duty.

In describing the operation of the system as a whole 1 will refer to thedrawings as a whole, wherein are illustrated a central station and twoterminal and one intermediate subscribers stations, all clearlydesignated. It will be assumed that there are at the central station oneor more series ofline-wiressay fifty in eachand that all theswitch-boards'are capable of switch-cord connection for placing thesubscribers ofany one series of wires in com munication with those ofthe same or any other series. For each series a listening operator atits telephone D is required. A switchman can ordinarily attend to theswitch-boards of more than one series. An observer to watch thegalvanometers A sets the hand-indicators A and conducts the preliminaryoperations for attaining a registration of service, both as regards timeand number of calls. Thennmber ot'switchmen and observers at a centralstation may therefore be graded by experience according to the extent ofits business. In some cases the observer and switchman may be combinedin one person. For conducting the business in silence a set of blanks isrequired. One bearing the words Connect it it with it another Disconnectbars No. It a time grade of service is desired, both should have, inaddition, Bars No. and Time printed thereon. For the best results as todispatch and convenience, subscribers should call by their predeterminednumber, although their names may be used instead. \Vith the listeningoperator at telephone D, the switchman in front of his switch-board, andthe observer within reaching distance, a subscriber at either stationlifts his telephone from the hook on the switch-Fever and calls direct:Connect 25 with 50. The listening operator writes those numbers on ablank for that purpose, or names if they be used, and hands it to theswitchman, who then taps the key a, which communicates with 50 asutlicient number of times to insure a response if he is available, andthen with a switch-cord couples the 25 and 50 wires via their switchesand any one of the unoccupied pairs of connecting-bars A, thegalvano-indicator of those bars showing whether response is being made,and, if not, further taps on the key will bein order. If 50, on beingcalled, lit'ts his telephone from its book, he finds himself in directtelephonic communication with the party (25) who called him. Theobserver, on noting the position of the galvanoindicator, then moves thehand-indicator to the one side, disclosing the number .of the set ofbars in service, showing the switchman at a glance which bars are openfor use or are occupied. The switchman having handed the blank to whichresponse has been made to the IIO observer, he notes thereon thctinie ofday and nals to be operated on any of the circuits from places the blankon a spindle-file. When the the central office;

galvano-indicator shows termination of service, the observer writes intoa blank Disconnectbars No.1, which is handed to the switchman. Thehand-indicator is then set back to cover its number, showing that saidbars are again open for use. i The switchman places said disconnectblank on a spindle-file, first noting time thereon, ifdesired,and soon,without requiring a word for conducting the business. Should thelistening operator require to orally communicate with partiescalling-as, for instance to respond O. K, on receiving a call, or forstating that No. 50 does not connectit would constitute the only talkingrequisite at the central station, and the absence of loud calling andother conversation enables the listener to more accurately perform hisduties. On the relief of each set'of operatives the blanks are reversedin position on the files and handled singly for registration either byassorting them for preservation or by special entry for each daysservice. Should any two or more subscribers simultaneously call, thelistener has only to call out: One at a time, Goon, 50, or such numberas he has been able to fully catch, and so on until all are disposed of.The connections between two or more central stations and theirrespective subscribers can readily be effected by means of a series ofstationwires, each wire being numbered, so that by telephone order maybe given from either central station for connection at any other of asubscribers wire of a certain number with a specified station-wire,which is then connected with the calling party via the connectingbars A.

Having thus described my invention, Iclaim as newand desire to secure byLetters Patent- 1. In a telephonic exchange system, aseries ofiudependent subscribers wires or circuits, all branching out from andnormally in connection with a receiving-instrument at a central office,but adapted to prevent the currents, or a too great portion thereof,from being diverted from the circuit through said central instrumentinto the branch circuits not in use, and provided with apparatus toreceive and enable signals to be made from said central office.

2. In a telephonic exchange system, a series of closed circuitscentering in and passing through a single central instrument, andresistance in the said circuits,to confine the electric currents, or themain portion thereof, in the circuit passingthrough saidcentralinstrument.

3. In a telephonic exchange system, a series-- of circuits, all unitingand passing through a single central instrument and adapted to confinethe main portion of the current to the circuit passing through thecentral instrument, combined with electric switches adapted to beoperated from the central office to close the distant end of saidcircuit through a suitable connection to ground, to enable the usualsig- 4; The combination, substantially as hereinbefore described, of aseries of wires for telephonic communication with one or moresubscribers on each, and 'radiatin g from a single ground-wire at acentral station, with a listening-telephone connected with saidground-wire and a high resistance near the outerterminus of eachsubscribers wire.

5. A telephonic exchange system embodying, substantially as hereinbeforedescribed, a series of subscribers wires, a telephone, a highresistance, and a signaling apparatus at the outer terminus of eachwire, and a central station having a ground-wire and a' listeningtelephone common to all of the subscribers wires, in combination with asuitable battery or its equivalent and means for applying the electricpower thereof to any and all of the subscribers wires for overcoming thehigh resistances-thereon and operating the calling-signal.

6-. The combination, substantially as hereinbefore described, of aseriesof telephonic subscribers wires radiating from a central station,and provided in each case with a subscribers calling apparatus locatednear the outer terminus of the wire and between-a high resistance andground, with means at the central station for attaining an electricpower to overcome said high resistances and means for applying saidpower to any and all of the wires in the series for operatingsubscribers signals.

7. In a telephonic exchange system involving a series of subscriberswires or circuits branching from a ground-wire common to all thesubscribers wires, a high resistance located near the end of eachsubscribers wire, as and for thepurposes specified.

8. In a telephonic exchange system involving a series of subscriberswires or circuits branching from a ground-wire common to all of them, acalling-signal near the outer end of each subscribers wire, a highresistance, and a relay operating as a switch for cutting out saidresistance, as and for the purposes specified.

9. ()n a telephonic line-wire provided at its outer terminus with a highresistance, the combination of a spring switch-lever maintained in adepressed position by the weight of a telephone thereon,and a switch toground, which is automatically controlled by the switch spring-leverwhen loaded with or released from the weight'of the telephone,substantially as described.

10. At a central station in a telephonic exchange system, theconnecting-bars, constructed in pairs, coupled together and to abattery, substantially as described,whereby the power of said battery isplaced on any twosubscrib- IIO ers wires when coupled by theconnectingwith means-such as connecting-bars and conducting-cords-forconnecting subscribers lines with each other, so that in connecting saidlines by the aforesaid means the electric indicator and battery areincluded in the circuit, as set forth.

12. The combination, with subscriberslines having each a high resistanceat the end and a telephone-switch of ordinary or suitable constructionfor cutting out the said resistance and connecting in the telephone, ofa battery, an electric indicator, and means-such as conmeeting-bars andconducting-cords-for connecting subscribers lines, said indicator andbattery being connected with the said means, as indicated, so that whenthe subscribers lines GEO. B. SCOTT.

Witnesses:

B. M. VREELAND, RALPH W. Porn.

